1. Field of the Invention
The invention relates to an arrangement for mounting an optical element, in particular in an EUV projection exposure apparatus.
2. Prior Art
Microlithography is used to produce microstructured components such as, for example, integrated circuits or LCDs. The microlithography process is carried out in a so-called projection exposure apparatus having an illumination device and a projection lens. The image of a mask (=reticle) illuminated via the illumination device is in this case projected via the projection lens onto a substrate (e.g. a silicon wafer) coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection lens, in order to transfer the mask structure to the light-sensitive coating of the substrate.
In a projection exposure apparatus designed for EUV (i.e. for electromagnetic radiation having a wavelength of less than 15 nm), owing to light-transmissive materials not being present, mirrors are used as optical components for the imaging process. The mirrors can be fixed e.g. on a carrier frame and can be configured such that they are at least partly manipulatable, in order to enable a movement of the respective mirror in six degrees of freedom (i.e. with regard to displacements in the three spatial directions x, y and z and also with regard to rotations Rx, Ry and Rz about the corresponding axes). In this case, it is possible to compensate for changes in the optical properties that occur for instance during the operation of the projection exposure apparatus e.g. on account of thermal influences.
WO 2005/026801 A2 discloses, inter alia, using three actuator devices in a projection lens of an EUV projection exposure apparatus for the manipulation of optical elements such as mirrors in up to six degrees of freedom, the actuator devices each having at least two Lorentz actuators and two actively drivable movement axes. The Lorentz actuators each have two elements which are separated via a gap and one of which has a solenoid, to which an electric current can be applied in order to alter the gap, such that the two elements of the Lorentz actuator, of which one is connected to the respective optical element or mirror and the other is connected to the housing of the projection lens, can be moved relative to one another, wherein the two elements of the Lorentz actuator are mechanically decoupled on account of the gap situated between them. Furthermore, a weight force compensation device embodied as a spring element, for example, is provided in order to minimize the energy consumption of the active or controllable actuating elements, since the weight force compensation device substantially carries the mass of the optical element or mirror, such that no permanent energy flow with associated generation of heat is necessary in this respect. The weight force compensation device (also designated as “MGC”) can be set to a certain holding force that is transmitted to the mirror via a mechanical element (pin) that couples mechanically to the mirror.